The invention pertains generally to coiled tubing reels used in conjunction with coiled tubing injectors for performing well servicing and coiled tubing drilling operations.
Continuous pipe, generally known within the industry as coiled tubing since it is stored on a large reel, has been used for many years. It is much faster to run into and out of a well bore than conventional jointed straight pipe since there is no need to join or disconnect short segments of straight pipe.
Coiled tubing xe2x80x9cinjectorsxe2x80x9d are machines that are used to run continuous strings of pipe into and out of well bores. The injector is normally mounted to an elevated platform above a wellhead or is mounted directly on top of a wellhead. A typical coiled tubing injector has two continuous chains. The chains are mounted on sprockets to form two elongated loops that counter rotate. The chains are placed next to each other in an opposing fashion. Tubing is fed between the chains. Grippers carried by each chain come together on opposite sides of the pipe and are pressed against it. The injector thereby continuously grips a length of the tubing as it is being moved in and out of the well bore. Examples of coiled tubing injectors include those shown and described in U.S. Pat. No. 5,309,900, and U.S. applications Ser. Nos. 09/070,592 and 09/070,593, all of which are incorporated herein by reference.
A coiled tubing reel assembly includes a stand for supporting a spool on which tubing is stored, a drive system for rotating the reel and creating back-tension during operation of the reel, and a xe2x80x9clevel windingxe2x80x9d system that guides the tubing as it is being unwound from and wound onto the spool. The level winding system moves the tubing laterally across the reel so that the tubing is laid across the reel in a neat and organized fashion. The coiled tubing reel assembly must rotate the spool to feed tubing to and from the injector and well bore. The tubing reel assembly must also tension the tubing by always pulling against the injector during normal operation. The injector must pull against the tension to take the tubing from the tubing reel, and the reel must have sufficient pulling force and speed to keep up with the injector and maintain tension on the tubing as the tubing is being pulled out of the well bore by the injector. The tension on the tubing must always be maintained. The tension must also be sufficient to wind properly the tubing on the spool and to keep the tubing wound on the spool. Consequently, a coiled tubing reel assembly is subject to substantial forces and loads.
A guidance arch extends from the top of the injector to provide a supported arched path to direct the coiled tubing leaving the tubing reel into the top of the injector. Alternately, as shown in U.S. Pat. No. 5,660,235, the reel can be positioned on top of the injector so that tubing is fed in a straight line into the top of the injector.
Historically, tubing reel assemblies have been shipped to wells with the required coiled tubing wound on the spool, and the spool installed in the reel assembly. Such spools are specially designed for the particular reel assembly and not meant to be disconnected or removed from the reel assembly during normal operation. A second reel assembly would therefore also have to be sent if there was need for different diameter tubing or in the event that replacement tubing was required. Alternately, if replacement tubing was required, a shipping spool could be used to transport replacement tubing to the well. A lightweight spooling stand would then have to be used to support the shipping spool to transfer the tubing onto the spool of the working reel assembly. To save weight and size, these shipping spools did not possess the structure necessary to handle the loads typically imposed on reels during coiled tubing operations. Rather, shipping spools were designed as a relatively inexpensive means of transporting the tubing from a factory to a well. Therefore, transferring tubing from the shipping spool to the working reel assembly was necessary.
Transferring tubing from a shipping spool to a working reel induces extra strain in the tubing as it is unwound from the shipping spool then rewound onto the working spool. Since metal tubing is plastically deformed during spooling, transferring coiled tubing from a shipping spool to a working reel assembly reduces the life or number of hours that the tubing can be used, thus increasing the cost of coiled tubing operations. Furthermore, transfers typically involve spooling 20,000 to 25,000 feet of tubing at rates of 100 to 200 feet per minute. Therefore, considerable time is required to complete a transfer.
There exist coiled tubing reel stands for receiving common and ordinary shipping spools for use as working reels. These tubing reel assemblies require inserting a shaft through the center of the spool, and inserting a pair of driving knobs, mounted to a drive plate on the stand, into the side of the spool to provide the connection for the drive system. As a consequence, this type of reel stand has several problems. First, the reel stand either has to be separable into two halves so that the sides of the stand can be moved laterally away from each other, or has to have the sides of the stand capable of being swung outwardly, in order to allow the shipping spool of tubing to be loaded on the stand. Second, the spool has to be carefully aligned with the drive system on the stand. Spools wound with tubing are very large and heavy, weighing 30,000 to 60,000 lbs. on average. They are cumbersome and difficult to maneuver. Consequently, aligning a spool and the drive system on a rocking ship or in high winds is a difficult task. Third, as previously mentioned, standard and ordinary shipping spools are not built to handle the substantial loads encountered by a typical working spool.
Other types of reel assemblies require that the drive system be partially dismantled to allow removal of the spool. Additionally, if different size tubing is used, the level winding system also has to be partially dismantled to change sprockets and other drive components to provide proper spooling of the tubing. Changing the drive system and level winding system components are difficult and time consuming.
The invention overcomes difficulties found in the currently available systems by permitting more rapid replacement of spools on tubing reel assemblies. Transfer of coiled tubing from a spool used for shipping or transportation to a working reel assembly can be avoided.
In accordance with the invention, a coiled tubing spool is used as both a shipping spool and a working spool. The spool, once transported to a site, is xe2x80x9cdroppedxe2x80x9d or lowered into a tubing reel assembly stand that is set up to rotate the spool. The stand includes two axles. The spool includes a support hub on each side. A slot defined in each support hub receives the ends of the axles as the spool is lowered into the stand. Each slot is then closed to capture the axle. As the spool is being lowered, a rotational coupling for turning the reel is simultaneously formed by a coupling member on the stand or spool sliding into engagement with a complementary coupling member of the other of the stand or spool. A power source on the stand rotates this coupling.
The invention has the advantages of allowing a spool wound with coiled tubing for a coiled tubing injector to be mounted to, and dismounted from, a stand, and coupled and uncoupled to a rotational power source, in a comparatively quick, convenient and reliable manner, with less manual activity and movement of mechanical coupling members. The stand need not be separated or disassembled, and the sides need not be moved laterally to accommodate the spool. Tubing spools can therefore be quickly changed as needed, with less potential for problems arising during changing. Additionally, a rotational coupling having one part mounted to a drive system located on a support stand and another part located on the tubing spool permits each spool to be fitted with the same type of coupling member, even if the spools have different diameters. The larger the coiled tubing diameter, the larger the spool""s diameter must be. Stands can therefore be designed to handle a variety of different tubing spools, thus allowing strings of tubing to be moved from one location to the another without having to move the stand. Reel assembly stands can also be maintained, if desired, at multiple locations, and tubing of different sizes be shipped between locations on spools that can be used as working spools. The invention further permits, if desired, the stand to be made relatively compact, and not much wider than the width of the reel. The compact width of the stand allows for more tubing to be shipped legally across public roads that have width restrictions.
In a preferred embodiment of a coiled tubing spool and stand according to the invention, a coiled tubing spool includes a plate-like hub on at least one side. A slot is formed in the plate for receiving the end of an axle extending from the stand. A catch automatically closes the slot once the axle slides to the closed end of the slot. The catch may also be normally closed and automatically opened by insertion of the axle into the slot. A stand includes a drive plate corresponding to the plate on the spool. At least one of the two plates includes a tab located along its periphery that slides into another slot formed along the periphery of the other drive slot as the reel is lowered into the stand. With the tab and slot located some distance from the axle, on the edges of the plate, greater torque may be applied to the reel.
In accordance with a different aspect of the invention, a level wind system for a reel assembly includes a compact cartridge that can be easily removed and replaced to change the gearing ratio of its drive system. The drive system is coupled with a rotational power source on a coiled tubing reel assembly stand for turning a spool so that the level winding system and spool operate synchronously. The cartridge thus allows quick and accurate alteration of the level winding system""s tracking speed to match the diameter of the loaded tubing.
One or more exemplary embodiments of a coiled tubing spool and stand combination for a coiled tubing injector system, in accordance with the invention as set forth in the claims, are described below in reference to the accompanying drawings. Additional advantages of various aspects of the exemplary embodiments will be identified in or are apparent from this description.